Just wanting some advice. My MIL gave us some really nice sleepsuits. They are all 100% polyester fleece. I normally put him in cotton sleepsuits with a sleeping bag at night. Is it ok to put him to sleep in a polyester one with a cotton vest underneath and if so, should I leave him out of his sleeping bag or is it ok to put him in that too. I want him to be warm enough in this cold weather but am worried that his skin cannot breathe through the polyester and he will overheat. Am I worrying unnecessarily or should I be wary of putting him in them?